1. Field of the Invention
This invention pertains to a device for washing, thickening and/or classifying fluid-borne solids. An example of its use is washing and thickening deinked fibers used in pulp and paper waking. The washer uses a rotary joint with alternating rows of stock sprayers and wash fluid sprayers directed toward a stationary conical screen.
2. Description of the Prior Art
In the prior art, it is well-known to use belt-type, drum-type and other washers for washing and thickening solids in amongst others, the mining industry, industrial and municipal waste treatment and in the paper manufacturing process, particularly to remove fines, inks and fillers from the deinked stock.
In belt-type washers and thickeners, it is well-known to spray stock into the nip of a high speed roll and fabric. Centrifugal force causes the fine fractions, including contaminants and excess, liquid to pass through the fabric with the washed stock retained on the surface. Doctor blades are then used to remove the washed stock from the high speed rolls.
In drum-type washers and thickeners, whether gravity or vacuum based, it is well-known to allow the fine fractions, including contaminants and excess liquid to pass through the fabric or drum.| washed and thickened stock is couched from the drum. Many prior: art drum washers have multiple stages.
U.S. Pat. No. 5,259,955 entitled "Vacuum Strainer" to Bolton, the present inventor, uses a conical screen as a filter for solids and liquids within a common stream, but is different from the present invention in the manner in which the incoming stock is applied to the screen. U.S. Pat. No. 5,453,193 to Maher et al., entitled "Strainer", commonly assigned with the present application, uses an overflow weir to deposit incoming stock. A weir will not uniformly distribute the feed flow at feed consistencies encountered in many washing, thickening and classifying applications. Moreover, the present invention allows for higher flow rates per unit screen area.